冈底斯成矿带西段则不吓铅锌矿床钾长花岗斑岩年代学、地球化学及地质意义  

Geochronology,geochemistry and geological significance of the K-feldspar granite porphyry from Zebuxia Pb—Zn deposit,Xizang(Tibet)

作　　者：杜保峰 何凯[2] 杨长青[2] 蔡志超[2] 鲁培庆[2] 耿爱宾[2] DU Baofeng;HE Kai;YANG Changqing;CHAI Zhichao;LU Peiqing;GENG Aibin(China University of Geosciences(Beijing),Beijing,100083;Henan Institute of Geological Survey,Henan Key Laboratory of Metal Mineral Mineralization Geological Processes and Resource Utilization,Zhengzhou,450001)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]河南省地质调查院,河南省金属矿产成矿地质过程与资源利用重点实验室,郑州450001

出　　处：《地质论评》2022年第6期2075-2088,共14页Geological Review

基　　金：中国地质调查局项目(编号:121201010000150014-17)的成果。

摘　　要：则不吓铅锌矿床位于冈底斯成矿带西段,西藏谢通门县境内,矿区发育大量钾长花岗斑岩,其与铅锌成矿存在密切联系。通过对其开展岩石学、LA-MC-ICP-MS锆石U-Pb年代学和岩石地球化学研究,探讨区内钾长花岗斑岩岩石成因、侵入时代及其与铅锌成矿之间的关系。岩石地球化学结果显示,钾长花岗斑岩具高硅、富钾而贫镁特征,A/CNK值介于1.08~1.38之间;REE具有较明显中等负Eu异常,总体呈现右倾的轻稀土富集特征,微量元素富集Rb、K、U、Th、Pb等大离子亲石元素,而Ba、Sr和Nb、Ta、Ti、P等高场强元素相对亏损。岩石地球化学研究表明钾长花岗斑岩属分异的S型花岗岩。锆石U-Pb测年结果显示,钾长花岗斑岩侵位年龄为14.18±0.15 Ma,系中新世岩浆作用产物,与印度—亚洲大陆碰撞后伸展背景下的引张构造有关,并与冈底斯成矿带中新世大规模斑岩侵位时代和相关斑岩型铜(钼)矿化时代一致,可能具有相同的成岩成矿环境,这为在该成矿带西段寻找与斑岩有关的铅锌矿床提供了参考。Objectives:The Zebuxia Pb—Zn deposit is located in the western of Gangdese porphyry Cu—Mo—Polymetallic metallogenic belt,Xizang(Tibet),which occurs lots of K-feldspar granite porphyry.In order to find out formation age and genetic types of the K-feldspar granite porphyry,further discuss diagenetic environment and the relationship with Pb—Zn mineralization.Methods:Detailed geological survey,LA-MC-ICP-MS zircon U-Pb dating and the whole-rock geochemical analysis of K-feldspar granite porphyry.Results:Zircon U-Pb geochronology results show that the K-feldspar granite porphyry was formed in 14.18±0.15 Ma pertain to magmatic products of the Miocene.Major elements of the K-feldspar granite porphyries have characteristics of enrichment silica and alkali,depleted magnesium,A/CNK ranges from between 1.08 to 1.38.Rare earth elements have the right-leaning pattern of the LREE enrichment and medium negative Eu abnormality.Trace elements are rich in Rb,Th,U,K and Pb,but which are poor in Ba,Sr and HFSE,such as Nb,Ta,P and Ti.Conclusions:K-feldspar granite porphyries have the differentiation characteristics of S-type granite.The Kfeldspar granite porphyries were probably formed in post-collision extensional setting background followed the Indian—Asian continental collision,and consistent with the epoch of the massive porphyry emplacement period and associated porphyry copper(molybdenum)mineralizatio of Gangdise metallogenic belt in the Miocene,namely they may have the same diagenesis and mineralization environment.In addition,it provides theoretical and practical basis for prospecting porphyry-related Pb—Zn deposits in the western part of the Gangdise metallogenic belt.

关 键 词：锆石U-PB测年 地球化学 钾长花岗斑岩 中新世 则不吓 冈底斯成矿带 

分 类 号：P618.4[天文地球—矿床学]